I been there and am kinda there again buddy. It happens especially if you put all your eggs into the SEO basket these days. I hit a really low low back in the rebill days when I went from just learning PPC to finding the best places to advertise diet offers before most experienced PPC guys and in turn made a boatload in about 6 months. Then since most of it was through Google and big G said fuck you affiliates we dont need you anymore even though you built our company...i had my 3 accounts terminated and lost pretty much all my income. At this point I was so new I didn't even know how shady some of these rebill merchants were.
I hit a depression which I have never had before and developed anxiety for the first time in my life. I used to kinda of be like GTFO when people said they were anxious and now I know why they said and did the things they did. Anxiety and panic attacks are something I would not wish on anyone. I still have anxiety issues stemming from hitting a high so fast and falling to zero so fast.
It took me some time to get over this....probably a good 6 months. I then got back to basics and what I did to get where I was and re-evaluated the offers I promoted and my own ethics now that I had all the information with what was going on. It took a good year to rebuild, but I did it successfully and continued to grow until last year.
SEO hits and even the rearrangement of the way PPC ads were displayed and the major influx of product picture ads had impact on my PPC too. Basically, my gross revenue was cut by about 60%-70%. Oh and I got lazy too which I promise myself will not happen again considering I hope to start a family this year. This in part was due to a back injury from a car accident and my growing love for opiates which I am also trying to shake atm because they make me lazy just as my smoking of oil which also needs to stop. I am in the process of re-evaluating again and figuring out how to minimize risk and spend money more efficiently on marketing online and looking at options offline now as well.
Look back at what you did and how you can better it this time around. Write a new business model/plan and execute. You will be good man. As someone else said....if you have the brains and talent to get there in the first place, you can do it again!
Good luck bro!